Add API endpoint to show all available search models.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

mayan/apps/dynamic_search/classes.py

@@ -47,6 +47,10 @@ class SearchModel(object):
         self.permission = permission
         self.__class__.registry[self.get_full_name()] = self
 
+    @property
+    def pk(self):
+        return self.get_full_name()
+
     @property
     def model(self):
         if not self._model: